The invention proceeds from a device for the external cooling of an electrical drive motor of a centrifugal pump unit.
With centrifugal pump units which for example are applied for the delivery of waste water in hollows, wells or likewise, the leading away of the dissipated heat of the electrically dry-running drive motor is effected via the motor outer surface into the surrounding medium. The centrifugal pump unit is as a rule with the motor above the pump, assembled in the hollow or well and at the beginning of the delivery as a rule is completely submerged into the waste water. After a certain delivery time the motor protrudes from the waste water, and specifically when the level of the water has sunk correspondingly lower. Since the unit is driven in the on-off switching operation, with short running times normally no problems occur.
The situation is different when the units are to be set up dry, i.e. are not to be operated submerged. Since with e.g. motors designed closed for explosion-protective reasons, the motor cooling surfaces increase with the second power of the dimensions, but however the power of the motor increases with the third power, the limit of the application of these units with the removal of the dissipated heat to the surrounding air alone is very quickly reached.
Furthermore it is known to provide the drive motor on the outside with a jacketing surrounding it at a distance and to let the intermediate space thus formed be flowed through by a part flow of the pump delivery flow, which is known as so-called hood cooling. This manner of cooling is suitable however only for delivery mediums which do not contain any dirt components or other fine admixtures or impurities, since otherwise the flow accesses and exits on the pump side get blocked and the hood cooling becomes ineffectual due to this.